I'm planning a trip to Croatia at the end of March/early April and would appreciate any advice from people, both herping and general Croatia advice.

Which are the best parts of the country to be based in to bump into the best range of species? Popping into Slovenia for an Olm would be pretty great so North East seems most likely but I'm open to ideas. Which areas are best for wandering around? Any other advice on mammals, birds, plants or anything would also be appreciated